1. Field of the Invention
The present invention relates to an inkjet head having pressure chambers arrayed in a matrix.
2. Description of the Related Art
JP-A-2003-237078 discloses an inkjet head having a large number of pressure chambers arrayed in a matrix. FIG. 11A is a schematic view of nozzle arrays when the inkjet head disclosed in JP-A-2003-237078 is used as a line head. In the inkjet head shown in FIG. 11A, sixteen nozzles are present in each belt-like region R delimited by a large number of straight lines extending in a paper conveyance (sub-scanning) direction. As for the sixteen nozzles 108, the coordinate in a head longitudinal (main scanning) direction and the coordinate in the paper conveyance (sub-scanning) direction differ from one nozzle to another. When the sixteen nozzles 108 are projected from the sub-scanning direction onto a virtual straight line extending in the main scanning direction, sixteen projective dots are obtained. The sixteen projective dots are separated at equally spaced intervals corresponding to a printing resolution. Assume that the sixteen nozzles 108 are numbered (1)-(16) in order from the nozzle whose corresponding projective dot is leftmost. Then, the sixteen nozzles 108(1), (9), (5), (13), (2), (10), (6), (14), (3), (11), (7), (15), (4), (12), (8) and (16) are arranged in that order from below. When each belt-like region R is divided equally into four small regions r1, r2, r3 and r4 by straight lines extending in the sub-scanning direction, four nozzles 108 are arranged on a straight line in each small region. Each belt-like region R includes one and the same array pattern of sixteen nozzles 108.
When ink is ejected at short ejection intervals sequentially from each nozzle 108 in such an inkjet head, a large number of straight lines extending in the sub-straight line can be printed so as to be separated at equally spaced intervals equal to the intervals of the aforementioned projective dots as shown in FIG. 11B. Because of the narrow intervals between adjacent ones of the straight lines, the range where the large number of straight lines are printed is observed actually as if it were a filled region.